Volcanoes are cone shaped hills or mountains that are formed near a vent that is connected to a reservoir of molten rock, or magma. The meaning of the word volcano is the vent that molten rock, gases, and solid objects are expelled from the earth. Whe the pressure deep inside a volcano is strong enough, then an eruption occurs. During an eruption, magma, tephra, and other materials are forced out of the volcano.
Some eruptions are mild, but others are violent and dangerous. During a mild eruption only ash and smoke might exit the volcano. Violent eruptions send large boulders and rocks crashing down the side of the volcano along with extemely heated ash and gases. Ash and other debris from the volcano can extend high into the atmosphere and spread over hundreds of miles away.
